This invention relates to a process for the preservation of plant embryos.
Numerous species of plants may be preserved and stored in the form of cell suspensions, calluses or even meristems.
The storage of plant embryos is justified in many cases, for example for regulating the production of plantlets where it is seasonal or for maintaining a clonal line. The preservation of plant embryos can have various advantages, including for example the possibility of temporarily stopping the development of the embryos, the time required for their transport to the seed bed or for their storage and the possibility of producing artificial seeds.
Somatic embryos have certain advantages for the multiplication of plants. They emanate in principle from a single cell and give genetically identical plants. From the beginning of their formation, somatic embryos have a bipolar structure: they have the two, meristems i.e., stem and root necessary to produce a plant. Accordingly, somatic embryogenesis appears an interesting alternative for the propagation of plants. It could be used for the rapid multiplication of species that are expensive to produce or of high-performance individuals emanating from in vitro cultures or of transformed plants that are difficult to reproduce sexually for example.
There are various known processes for storing undifferentiated tissues at low temperatures and/or under hypoxia. Generally speaking, the tissues are kept on a semi-solid medium or are stored at a temperature below 0.degree. C.
One known process comprises storing grape calluses at a temperature of 10.degree. C. or 15.degree. C. To increase their storage life, a layer of silicone oil may be added to the calluses, although they remain on their nutrient substrate. Another process which may be applied to yeasts or cells comprises forming an aqueous emulsion of the cells using an oil medium and cooling the whole to a temperature of the order of -20.degree. C.-30.degree. C. so that the water remains supercooled. The oil thus acts as a cryoprotective agent, for the cells or yeasts.